1. Field of the Invention
The invention relates generally to roller bearings, and more particularly to roller guides such as retainers and guide rings used in roller bearings to hold and position rolling elements.
2. Reference to Prior Art
Examples of self-aligning angular contact roller bearings are provided in U.S. Pat. No. 2,387,962 issued Sep. 28, 1942, U.S. Pat. No. 2,767,037 issued Oct. 16, 1956, and U.S. Pat. No. 4,557,613 issued Dec. 10, 1985. In each of those patents the illustrated roller bearing includes an inner ring that provides a substantially spherical inner race surface, an outer ring having a pair of outer race surfaces with convex curvatures, and a pair of oppositely axially inclined rows of symmetrical, hourglass-shaped rollers. Another example of an angular contact roller bearing is illustrated in U.S. Pat. No. 3,912,346 issued Oct. 14, 1975. That roller bearing includes oppositely axially inclined rows of symmetrical, barrel-shaped rollers.
The foregoing roller bearings also include roller cages or retainers to separate, guide and position the rollers in each row. Each of the retainers includes a set of axially extending webs or prongs that circumferentially separate the rollers in one of the rows and a set of oppositely axially extending prongs that circumferentially separate the rollers in the other row. A disadvantage associated with known roller retainers such as those used in the aforementioned patents is that they fully separate the rollers and occupy space within the bearing unit and between the rollers that could otherwise be used for additional rollers and/or additional lubricant.
Additionally, loads exerted on a bearing unit such as one of those described above are typically carried by the rollers in only one part of the unit at a time, that part being referred to as the "load zone". Especially where bearings are used in oscillatory applications, it is desired that the rollers in the bearing unit precess or index so that they are cycled through the load zone. Cycling the rollers results in utilization of the entire race surface of each of the rollers to extend rolling contact fatigue life. Cycling the rollers also redistributes lubrication within the bearing unit which in turn reduces fretting damage and improves the bearing unit's resistance to raceway corrosion. To cause such precessing or indexing of the rollers, it is known to use a retainer as described above but with prongs that define skewed roller pockets. In one known retainer design the prongs are inclined at an angle of about 4.degree. to provide an imbalanced amount of skew to the rollers. When the angle of oscillation is sufficiently large (i.e., at least 2.degree.-3.degree.) the skewed rollers will precess or index during oscillation of the bearing unit.
While a retainer with inclined prongs has advantages for initiating roller precessing or indexing, that retainer also occupies space within the bearing unit and limits the number of rollers that will fit in the unit, thereby limiting the load capacity of the bearing unit.